Shortsightedness or myopia and farsightedness or hyperopia are common refractive disorders of human eyes. Objects beyond a distance from a myopic person are focused in front of the retina, and objects beyond a distance from a hyperopic person are focused behind the retina, and consequently the objects are perceived as blurry images.
Myopia develops when the eye grows excessively larger than the focal length of the eye. Myopia usually progresses in human eyes over time and is typically managed by regularly renewed prescriptions of optical lenses such as corrective spectacles and contact lenses. Those lenses provide clear vision but do not retard progression of myopia. Undesirable sight-threatening eye diseases are also associated with high levels of myopia.
Hyperopia is usually congenital, when the size of the eye has not grown enough and is shorter than the focal length of the eye. Without proper management, hyperopia may associate with blurred vision, amblyopia, asthenopia, accommodative dysfunction and strabismus. Hyperopia is typically managed by prescriptions of corrective optical lenses which temporarily provide clear vision but do not heal or eliminate the disorder permanently.
Therefore, there is a need for new technology to reduce the economic and social burden produced by refractive disorders such as common myopia and hyperopia by providing clear vision and a retardation function at the same time. Recent scientific publications have stated that the dimensional growth of developing eyes is modulated by optical defocus, which results when images are projected away from the retina. Refractive development of the eye is influenced by the equilibrium between defocus of opposite directions. In particular, it has been documented that artificially induced “myopic defocus” (an image projected in front of the retina) may retard myopia from progressing further. In this context, the position of “in front of the retina” refers to any position between the retina and the lens of an eye but not on the retina.
WO 2006/034652, to To, 6 Apr. 2006 suggests the use of concentric multi-zone bifocal lenses in which myopic defocus is induced both axially and peripherally for visual objects of all viewing distances. Those methods have been shown to be effective in both animal study and human clinical trial for retarding myopia progression. However, those methods comprise the prescription and the use of specialty lenses which may not be suitable for all people. Similar disadvantages apply for the other contact lens designs such as U.S. Pat. No. 7,766,478 B2, to Phillips, published Aug. 3, 2010; U.S. Pat. No. 7,832,859, to Phillips, published 16 Nov. 2010; U.S. Pat. No. 7,503,655 to Smith, et al., published 17 Mar. 2009; and U.S. Pat. No. 7,025,460 to Smith, et al., published 11 Apr. 2006.
U.S. Pat. No. 7,503,655 and U.S. Pat. No. 7,025,460, both above, suggest methods to counteract myopia by manipulating peripheral optics, inducing relative peripheral myopic defocus without inducing myopic defocus on the central retina. Since it is known that the protective effect of defocus is directly correlated with the area of retinal area exposed to it, their design may not achieve maximum effectiveness as defocus is not induced on the central retina.
Accordingly the need remains for improved methods, apparatuses, and/or systems for inhibiting and potentially reducing or even curing refractive disorders of a viewer. Therefore it is an objective of the current invention which make use of novel viewing systems instead of specialty lenses, to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.